We are studying the sequence organization, transcription and control of heat shock genes of Drosophila and other organisms. Transcription of these genes is strongly induced by temperature elevation and certain other stimuli while transcription of previously active genes is depressed. We are developing cell transformation, nuclear injection, and in vitro systems for assaying transcription of cloned heat shock and other genes in order to identify and characterize sequences involved in their control. We are also studying sequence organization and evolutionary change in large cloned segments from heat shock loci of melanogaster, simulans, mauritiana, virilis, and pseudo-obscura, and are attempting to clone a human gene homologous to melanogaster hsp 70 gene.